Driven by concern about the steadily rising incidence of cancer, the Cancer Prevention and Education Society distinguishes itself from the majority of cancer charities in that its primary purpose is to prevent people from getting cancer in the first place, and its belief is that reducing exposure to chemicals in the environment is essential for achieving this goal.
Finding new therapies for people with the disease and providing support for patients during their illness are extremely important. We do, however, think too little effort has gone into really understanding why cancer rates are rising (see the charts below) and what more can be done prevent it, given that a third of people will get the disease during their life time.
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During our lives we are potentially exposed to thousands of carcinogens. For various reasons, these can be very difficult to identify (for more detail, see H&E#33, Standards of Evidence). We also live in a society requiring definitive proof of harm before actions are taken to redress problems, so even when they are clearly known it can take literally years before anything is done about agents which cause cancer, as was clearly demonstrated by the successful rear-guard actions fought by the asbestos and tobacco industries.
Although the identity of specific carcinogenic compounds remains unclear, we believe that rising incidence of the disease points to a change in the environment as a contributing factor in the overall increasing burden of cancer on society. Although age is a risk factor in cancer, age-adjusted cancer data clearly shows that, for any given age group, cancer is becoming more common; furthermore, cancer rates in children have been rising steadily over many years (Kaatsch et al. 2006; see also commentary in the British Medical Journal).
Most cancer prevention strategies focus on genetic factors, viruses and lifestyle choices such as smoking, drinking alcohol, lack of exercise and poor diet (see H&E#48, Opportunities for Cancer Prevention). Early diagnosis is often, confusingly in our opinion, also considered a prevention strategy.
While we agree these are important risk factors, we believe that the effects of man-made carcinogens have been seriously under-estimated and that insufficient efforts have gone into preventing human exposure to them, a position recently reinforced by the US President’s Cancer Panel report on cancer prevention.
We are therefore working to reduce the current epidemic levels of cancer and other diseases by educating people about the importance of reducing human exposure to carcinogens and other environmental chemicals which may cause disease.
Aims of CPES
Depending on who you speak to, somewhere between 45-100,000 chemicals are now in use. Of these, only about 1.5-3% have been tested for carcinogenicity. For other diseases, reliable tests have yet even to be developed.
The Society raises public and medical awareness about the potential risks which these substances pose. More needs to be done to limit human exposure to carcinogens in air, water and food and to make transparent exactly what we are being exposed to.
The Cancer Epidemic
We often hear that we are “winning the war” on cancer – and indeed there have been some noteworthy successes, such as in the treatment of testicular cancer and some blood malignancies, particularly childhood leukaemia. However, many cancers remain big killers, including melanoma, lung, colon, and breast cancer.
Males. According to the UK Office for National Statistics, the total incidence of cancer in men in England and Wales rose 31% between 1971 and 1999. Significantly reduced smoking and the subsequent decline in lung cancer in men offsets an otherwise general increase in cancer incidence: cancer incidence excluding lung and non-melanoma has risen 47% between 1971 and 1999.
Some cancers are rising alarmingly: melanoma, non-Hodgkin’s lymphoma, prostate, testicular, and multiple myeloma have increased by more than 100%. The incidence of prostate cancer now exceeds the incidence of lung cancer. Apart from lung, pancreas, stomach and Hodgkin’s, age-adjusted cancer incidence in males has been steadily rising.
Females. Again we see a worrying increase in cancer incidence for the period 1971-99. Excluding lung and non-maliganant skin cancers, overall age-standardised cancer incidence in females rose 38%. If we include lung cancer (since women have not given up smoking in the way men have) then the increase rises to 41%.
NHL, melanoma and kidney cancer have risen by more than 100%, consistent with the increase in men. Breast cancer has risen by 75%. Because the base rate for breast cancer is so high, the sheer number of women affected is of tremendous concern. Other than cervix, stomach and Hodgkin’s, age-adjusted cancer incidence in females has also been steadily rising.
Environment or Genes?
There has been considerable interest in the genetic causes of cancer for many years now. The theory is, if we understand which genes are responsible for uncontrolled cell division then it should give us clues to therapeutic interventions which can treat cancerous cells. In addition there is the notion that many cancers are genetically inherited and that the disease is therefore a problem of heredity.
However a landmark study of 90,000 Swedish twins published in 2000 has shown that the environment is the main cause of cancer. The study showed that if one twin got cancer the other did not necessarily get it, showing that environmental factors (here understood as non-genetic causes such as lifestyle factors, rather than causes fully external to the individual) are mainly to blame (Lichtenstein et al. 2000).
Further evidence comes from the discovery that Asian-American women born in the West have much higher risk of breast cancer than Asian-American women born in the East, a strong indicator that something unique to the Western environment is responsible for higher breast cancer risk (Ziegler 1993).
Dietary and lifestyle changes undoubtedly account for a proportion of this risk, but why it is that diets high in red meat should result in more cancer is as yet unclear; diet also only contributes a relatively small fraction to someone’s overall risk of cancer, 40% of which remains unexplained (Parkin 2011, also see this useful summary from the BBC).
No part of the globe is free of synthetic chemicals
Throughout the twentieth century, literally thousands of synthetic chemicals have been manufactured and released into the environment both deliberately (e.g. as pesticides) or as pollution (e.g. dioxin). They are also added to food, cosmetics, toiletries and household products, in particular cleaning products, where producers play on our fear of germs.
Many of these chemicals are truly artificial: their structure is novel and not found anywhere in nature. For example, chlorinated compounds such as the anti-bacterial triclosan, found in soaps and toothpaste, are truly man-made, a feature of our environment going back only 70 years or so.
Many of these substances are persistent and because they are not easily metabolised they accumulate in our bodies. An enormous group of such chemicals are the organochlorines which are made by chemically combining chlorine to carbon containing molecules. As a general rule, organochlorines are much more toxic than their unchlorinated analogues. Organochlorine compounds are found everywhere: tap water, dry cleaning fluid, disinfectants, cleaning products, toothpaste, pesticides, etc.
Huge quantities of man-made chemicals are entering the global ecosystem. It is estimated that there are about 35 tons of the pesticide atrazine in Lake Eyrie in North America. Poisoned Beluga whales have been washed up dead in the Canada’s St Lawrence river; some of these whales are so contaminated with pollutants from the river they qualify as hazardous waste under Canadian law.
Scientists looking for an unexposed control population to compare body burdens of chemicals between people looked at the blood and fat of indigenous populations living in the Arctic Circle. Instead of the expected low levels of synthetic chemicals among those living in the pristine Arctic, they found these people had some of the highest global levels of chemical pollutants in their bodies.
This contamination is explained by two factors; first, by a process known as “global distillation”, chemicals persistent in the environment accumulate in colder parts of the globe; secondly, these chemicals concentrate up the food chain. Since indigenous Arctic populations consume seal and whale meat, top predators highly contaminated with pollutants, they in turn become highly exposed to these chemicals.
The effects of chemicals on human health
From time to time there are well-publicised reports in the media about industrial accidents where large quantities of toxic chemicals are suddenly released into the environment. Seveso, Bhopal and Minamata have become synonyms for such accidents.
The effects of chronic, low dose ingestion of toxic chemicals on human health can however be much subtler, with researchers investigating a wide range of issues including the effect of pesticide exposure on birth weight (Rauch et al. 2012), BPA and childhood behaviour (Perera et al. 2012), perfluorinated compounds used in e.g. Teflon manufacture and obesity (Halldorsson et al. 2012), phthalates and childhood mental development (Whyatt et al. 2012), and pesticides and Parkinson’s disease (Wang et al. 2011).
Each one of us carries at least 250 chemical contaminants in our bodies. Many artificial chemicals evade metabolic degradation and accumulate in our tissues, particularly in body fat. Perhaps of greatest concern is that the breast feeding infant is right at the top of the food chain and residual toxics present in the mother pass across to the child in her milk. Thus a very important activity which provides essential nutrients to the growing child, confers immune protection and promotes bonding also becomes a source of toxic chemicals. This problem is made even worse because small children lack important de-toxification enzymes in the liver.
In looking at cancer in the general population it is very hard to determine the effect of the chemicals to which we are exposed because we are exposed to so many during our lifetime. One of the stronger correlations between chemicals and cancer has been seen in farmers where, for the last thirty years or so, there is evidence they are experiencing higher rates of leukaemia, non-Hodgkin’s lymphoma and cancers of the brain and prostate than the general population (e.g. Fragar et al. 2011, Parent et al. 2009). Animal and epidemiological studies have linked these types of cancer to pesticide and solvent exposures.
In the 1940s American farmers used about 22 thousand metric tonnes of insecticides. Now more than 450 thousand metric tonnes are used each year. 53 carcinogenic pesticides are registered for the use on major crops such as apples, tomatoes and potatoes. Approximately 34 pesticides are used for lawn treatment at rates up to five times greater than in agriculture. Furthermore, since 1976 several human studies have found a strong association between increased body levels of pesticides and breast cancer.
What can people do to reduce their chances of getting cancer?
A great emphasis has been placed in recent years on patient habits and lifestyle choices, and most of us have (rightly) been warned of the dangers of smoking and sunburn, the need to eat a healthy diet and the importance of exercise in keeping healthy.
However, there is a great deal more to cancer prevention than adopting a healthy lifestyle, because many of the causes of cancer remain unexplained, and many of the causes are things we can do very little about as individuals. Just as, for example, prohibiting smoking in public places has been important in eliminating an involuntary exposure to carcinogens, we are exposed to many chemicals in our environment whether we want to or not, in food packaging, pesticide residues, as air pollution, flame retardants and so forth.
Consumer choice means little here because information about which chemicals are used where is scant, the availability of alternatives is limited (and where they are available, information continues to be scant) and, besides anything else, the complexity of chemical exposures is so complicated that an individual has very little chance of making a meaningful decisions when it comes to deciding what they will allow themselves to be exposed to.
An inspection of just about any bottle of shampoo or similar product will reveal a host of ingredients, all of which serve a purpose (e.g. as foaming agents, surfactants, anti-bacterials, perfume, etc).
The current problem is that many items such as household cleaning products do not clearly reveal what chemicals are in them and nor are the producers required to do so for reasons of commercial secrecy. Labels reveal very little about the contents of a product; what is presented are often either codes or incomprehensible to most people.
It is therefore quite impossible for the shopper to make an informed decision about what he or she considers safe to buy. Given the lack of safety testing, the fact that the items are on the market does not guarantee their safety. How can the shopper possibly judge a product if he/she does not know what is in it?
We therefore need a strong regulatory framework which requires substances to have a strong pedigree of safety before they can be put into consumer goods and the environment. This is the only way the total chemical burden on people and the environment can be significantly reduced.
Colborn, Theo; Dianne Dumanoski; and John Peterson Myers. Our Stolen Future: Are We Threatening Our Fertility, Intelligence and Survival? A Scientific Detective Story. New York : Dutton, 1996.
Grossman, Elizabeth. Chasing Molecules: Poisonous Products, Human Health, and the Promise of Green Chemistry. Shearwater : 2009.
Thornton, J. Pandora’s Poison: Chlorine, Health, and a New Environmental Strategy. Cambridge, Mass. : MIT Press, 2000.